Boot-strap type driving circuits have been widely used to drive large capacitive loads such as decoders and data input/output circuits in memories. In such boot-strap type driving circuits, a potential at the gate of an output field effect transistor is raised above the power voltage through a boot-strap capacitor by a known boot-strap effect so that the output transistor is allowed to operate in the unsaturated region. That is, the output transistor can provide an output signal of the same value as the power voltage without any level reduction. Therefore, the boot-strap type driving circuit is suitable to drive large capacitive loads at a large amplitude and has been advantageously used in a variety of electronic systems.
However, in such boot-strap type driving circuits, it has been difficult to charge the output capacitor at a high speed, and hence the operational speed of boot-strap type driving circuits is low. The demand for high speed driving circuits is great, and thus, many attempts have been proposed in order to develop such high speed driving circuits. However, these attempts have been unsatisfactory.